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# EDR Calculations for master bedroom

Member Posts: 5
Hello, I am a college student and I have a project on calculating EDR for my room size. Could anyone give me a run through on how I would calculate the heat loss , and EDR of a Bedroom with 1 window and the room is 13.6x13.6x8. It also says 65 BTU per sf foot?

## Comments

• Member Posts: 23,880
Say what? EDR - equivalent direct radiation -- is a characteristic of whatever is heating the space -- radiator, baseboard, what have you. So the question is... what do you have in there?

It has nothing to do with heat loss -- except that you need enough radiation to compensate for the heat loss.

There are a number of on line ways for calculating heat loos -- one of the better is on Slant/Fin's website. Take a look at it...
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 8,542
What says 65 BTUs per Sq. Ft.?
You can google the Slant Finn heat loss calculator, plug in the needed info, room size wall dimensions, number of windows, number of outside walls, ceiling height, etc and that will tell you the heat loss for the room, in BTU's. You can then convert the BTU's to EDR. Divide the BTUs by 240 (BTUs in one EDR). That equals the total EDR needed.
• Member Posts: 5
Well, it’s 65 per sf for the project we are doing. I am confused also. Haha I am basically designing the radiators to fit each room and he also wants us to get the heat loss per room. My main question is, can I put as many radiators as I please in the room? (As long as it’s within reason) and not undersized?
• Member Posts: 23,880
65 BTU per square foot... of what? If it's per square foot of bedroom, either you are somewhere in Nunavut or Siberia, or someone is wildly off the mark.

If it's 65 BTU per EDR, someone is just plain wildly off the mark -- as @Fred said, on steam figure 240 BTU per EDR square foot; for hot water heat the value is lower -- since the radiator is cooler.

As to how many radiators you can put it... as many as will fit.

I'm very much afraid, though, that either you misunderstand the question -- or the question is exceedingly poorly put by your "professor".
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 2,112
It's possible that your teacher is hoping you will discover what and how EDR is used and applied as well heat loss calculations.
You should ask your teacher to clarify.
• Member Posts: 15,951
Multiply the square footage of your room x 65 to get the btu load. Divide that #/240 to get your EDR.

You can put as many radiators that you want to get the required EDR (it won't be exact). Information on this site can help you find the radiator sizes. Or look at Peerless boiler or Burnham boile web sites.

As far as the room heat loss you will have to calculate that. there are several ways. Software such as the Slant Fin app is one way. if your professor wants it old school you can use "manual J" or Carrier has information with the old HTM multipliers.

Doing it on paper the long way is more accurate. Software 'rounds off"

Be aware that the 65btu/square foot and your actual heat loss will not match
• Member Posts: 5
Yeah he actually wants us to use the manual J, I think I’m understanding more. He is just very vague when explaining things and made it sound like the heat loss and the edr go completely hand in hand. My teacher is very smart but doesn’t really know how to explain things to people who really have little to no idea what’s going on in the steam boiler world haha, but I’m working on it
• Member Posts: 15,951
To find the correct EDR you a heat loss of the space using Manual J Temperature difference between inside temp and outdoor winter temp (winter design TD). Measure floors area, wall area, ceiling area then get window and door area and subtract them from the wall area. Calculate heat transmission factors and multiply them out. Door and window area is calculated seperetley.

The conflict is the 65 btus/square foot. Maybe he wants you to use 65 btus/linear foot of outside wall to figure the infiltration load
• Member Posts: 8,542
Maybe he's looking to maintain 65 degree temp in the space on design day? Needs to be clarified for sure.
• Member Posts: 5
Does 207 EDR for a 1300 SF ranch home sound roughly correct?
• Member Posts: 23,880
Seems a little high -- but not completely outrageous.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 8,542
Doesn't sound to bad to me but I'm use to antique homes where the envelope isn't that well insulated or tight and windows are single pane with no storms.
• Member Posts: 5
Yeah this is a home based in Michigan not sure if that would change much but, I got roughly 200-210 by calculating my heat loss per outside wall in the room then divided that by 240 btu
• Member Posts: 2,112
That should be fine.
Be sure to bring up in class the discussion about EDR and heat loss.